Positioning servo controller

ABSTRACT

A positioning servo controller is provided in which optimization of the positioning state can be conducted simply by adjusting an adjustment gain. In a positioning servo controller with: a speed feedforward controlling section ( 22 ) which sets a value that is obtained by adding a first feedforward compensation amount to a position deviation, as a speed command; an acceleration feedforward section ( 23 ) which sets a value that is obtained by adding a second feedforward compensation amount to a speed deviation, as an acceleration command, the second feedforward compensation amount being obtained by amplifying a differential value of the first feedforward compensation amount; and a torque amplifier ( 3 ) in which an acceleration deviation is used as a torque command, and which drives a controlled object on the basis of the torque command, the values of the first feedforward gain and the second feedforward gain are values of functions in which the value of the adjustment gain is used as an argument.

TECHNICAL FIELD

The present invention relates to a positioning servo controller(position control apparatus) which performs positioning of a controlledobject, and more particularly a positioning servo controller forpositioning a motor.

BACKGROUND ART

FIG. 30 is a control block diagram showing the configuration of aconventional positioning servo controller. As shown in FIG. 30, theconventional positioning servo controller is configured by a positioncontroller 1, a speed controller 2, a torque amplifier 3, a motor 4, anda differentiator 5.

The positioning servo controller controls the position θ [rad] of themotor 4 in which the inertia is J [N·m·s²].

The motor 4 is provided with an encoder (not shown), so that theposition θ of the motor 4 can be detected by the encoder. A positiondeviation (θr-θ) between a position command θr which is supplied from ahigher-level unit (not shown), and the position θ of the motor 4 isinput to the position controller 1.

The position controller 1 is a proportional controller which outputs avalue obtained by multiplying the deviation with a position loop gain Kp[1/s], as a speed command ωr [rad/s] for the motor 4.

The differentiator 5 differentiates the position θ [rad] of the motor 4,and outputs the speed ω [rad/s] of the motor 4.

The speed controller 2 is a proportional controller which receives aspeed deviation between the speed command ωr [rad/s] and the speed ω[rad/s] of the motor 4, and which outputs a value obtained bymultiplying the deviation with a speed loop gain Kv [N·m·s], as a torquecommand Tref [N·m] for the motor 4.

The torque amplifier 3 receives the torque command Tref, and generates atorque Tr to drive the motor 4.

Namely, the positioning servo controller is used for causing theposition θ of the motor 4 to follow the position command θr. Theposition θ of the motor 4 is a position response with respect to theposition command θr.

In such a conventional positioning servo controller, the feedbackcontrol system in which a positioning control is conducted on the basisof the fed-back position response θ of the motor 4 is used.

As described above, usually, the positioning servo controller has thespeed loop process as a minor loop, in the position loop process.

In such a positioning servo controller of the feedback control system,however, the values of the position loop gain Kp and the speed loop gainKv are finite values and have the upper limit.

Therefore, the position response θ of the motor 4 fails to completelycoincide with the position command θr, and so-called servo delay occurs.

FIGS. 31(a) and 31(b) are the graphes showing the operation of theconventional positioning servo controller.

In FIG. 31(a), the position command θr and the position response θ areshown, and, in FIG. 31(b), differentials dθr/dt and dθ/dt of theposition command θr and the position response θ are shown.

As shown in FIGS. 31(a) and (b), dθr/dt is a command of accelerating themotor 4 at a constant acceleration, and, after the motor reaches asteady-state speed V [rad/s] and movement at the steady-state speed V isconducted for a predetermined time period, decelerating the motor at aconstant acceleration.

In this case, the position deviation is V/Kp [rad] at the maximum, andthe time period between a timing when the value of dθr/dt becomes 0 andthat when the position response θ actually reaches the value of theposition command θr is prolonged in proportion to 1/Kp [s].

FIGS. 31(a) and 31(b) show manners of variations of the commands θr anddθr/dt and the responses θ and dθ/dt in the case where theacceleration/deceleration time=0.1 [s], the steady-state speed V=100[rad/s], the predetermined time period=0.2 [s], the position loop gainKp=25 [1/s], the speed loop gain Kv=200 [N·m·s], and the inertia J=1[N·m·s²].

In FIGS. 31(a) and 31(b), the steady-state deviation is V/Kp=100/25=4[rad], and the time period between a timing when dθr/dt becomes 0 andthat when the value of the position response θ actually reaches that ofthe position command θr is 0.1 [s].

In such a positioning servo controller, in order to eliminate theabove-mentioned servo delay, the feedforward control system is sometimesused together with the feedback control system.

FIG. 32 is a control block diagram showing the configuration of apositioning servo controller in which the feedforward control system isused together with the feedback control system.

The positioning servo controller comprises feedforward controllers 6 and7 in addition to the components of the positioning servo controller ofFIG. 2.

The feedforward controller 6 receives the position command θr,differentiates the position command θr, and outputs a value which isobtained by multiplying the differential value with a first feedforwardgain Kff1 [1/s].

The value is a first feedforward controlled variable which is to beadded to the speed command ωr [1/s] that is output from the positioncontroller 1.

According to the configuration, in the positioning servo controller ofFIG. 32, the speed loop process is conducted on the basis of the speedcommand which is directly produced from the position command θr, andwhich does not contain a servo delay element. Therefore, the servo delaycan be further eliminated as compared with the case where only thefeedback control is used.

The feedforward controller 7 receives a first feedforward compensationamount output from the feedforward controller 6, differentiates thecompensation amount, and outputs a value which is obtained bymultiplying the differentiation with a second feedforward gain Kff2, asa second feedforward compensation amount.

The second feedforward compensation amount is added to the value outputfrom the speed controller 2, and the result of the addition is input asthe torque command Tr to the torque amplifier 3.

According to the configuration, the torque amplifier 3 can drive themotor 4 on the basis of the torque command Tr which does not contain aservo delay element.

As described above, in the positioning servo controller of FIG. 32,servo delay which may be generated by the feedback control can becompensated by conducting the speed feedforward control and the torquefeedforward control.

FIG. 33 is a control block diagram showing the blocks of the positioningservo controller of FIG. 32 in a simplified manner. As shown in FIG. 33,the control performance of the positioning servo controller depends onthe values of the feedforward gains Kff1 and Kff2.

In the positioning servo controller of FIG. 32, therefore, the motor 4is controlled in a state where the feedforward gains Kff1 and Kff2 areset to optimum values so that servo delay is reduced to a degree assmall as possible.

When the feedforward gain Kff1=1, the control block diagram of thepositioning servo controller is as shown in FIG. 34.

When the feedforward gain Kff2=J, the transfer function G from theposition command θr to the position response θ has a value of 1, andideally no delay occurs between the position command θr and the positionresponse θ, so that servo delay of the positioning servo controller is0.

In practice, however, it is often that physical quantities such as theinertia J of the motor 4 which is the controlled object are notcompletely grasped, and it is difficult to set the values of thefeedforward gains Kff1 and Kff2 to optimum values.

In such a case, during a process of positioning the motor 4, aphenomenon such as an overshoot or an undershoot occurs. When Kff2=J,for example, servo delay of the positioning servo controller is 0. Inthe case where the value of J is unknown, however, the value of thefeedforward gain Kff2 cannot be set to that of J, and hence an overshootor an undershoot occurs in the response.

FIGS. 35(a) and 35(b) show manners of variations of the speed responsedθ/dt which is a differential of the position response θ of thepositioning servo controller in the case where the value of thefeedforward gain Kff2 is not optimumly set.

In FIGS. 35(a) and 35(b), Kff2=0.5=J/2.

FIG. 35(b) is an enlarged view of the portion A in FIG. 35(a).

As shown in FIG. 35(b), an overshoot occurs in the speed response dθ/dt.

In order to eliminate such an overshoot, a countermeasure such as thatthe value of the feedforward gain Kff1 is reduced, or that a filter isdisposed in the output of the feedforward controller 7 has been taken.However, the conventional positioning servo controller has a problem inthat servo delay is again produced by such a countermeasure.

Returning to FIG. 30, the conventional positioning servo controller isconfigured by the position controller 1, the speed controller 2, thetorque amplifier 3, the motor 4, and the differentiator 5. Theconventional positioning servo controller controls the position θ [rad]of the motor 4 in which the inertia is J [N·m·s²].

For the sake of simplicity of description, it is assumed that thecontrolled object is a rigid body and the total inertia of thecontrolled object and the motor 4 is J, and also that the response ofthe torque amplifier 3 is so fast as to be negligible.

As described above, in the positioning servo controller, usually, aspeed loop having the speed loop gain Kv is disposed as a minor loop inthe position loop process. The torque amplifier 3 which generates atorque is disposed in the speed loop. The motor of the inertia J isrotated by the generated torque Tr. The position θ is read into thecontroller by the encoder to be used in the control. In such aconventional positioning servo controller, a machine is coupled to theend of the motor, and it is important to adjust the values of Kp and Kvin a well-balanced manner in accordance with the characteristics of themachine and the operation requirement use.

As shown in FIG. 36, the response characteristic in the case where astep command is input to the control system of FIG. 30 is variouslychanged depending on the combination of the values of Kp and Kv.

In FIG. 36, three kinds of lines, or lines (a) to (c) are drawn. Thelines respectively show response characteristics in the followingmanner:

(1) (a) shows the case where Kv=50 and Kp=10,

(2) (b) shows the case where Kv=100 and Kp=25, and

(3) (c) shows the case where Kv=50 and Kp=50.

It is assumed that J=1 in all the cases.

For example, the case will be considered in which the requestedspecification is that, as shown in the line (b) of FIG. 36, an overshootdoes not occur and a high response is attained, and the initial state isthe state of the line (a) of FIG. 36. When adjustment is to be conductedin accordance with the request, the value of Kp is first graduallyincreased while monitoring the waveform of the position feedback, and,when the state of the line (c) of FIG. 36 is attained, the value of Kvis then gradually increased. As a result, the state of the line (b) ofFIG. 36 is obtained.

In a usual case, when Kv is excessively increased, however, the servosystem oscillates because of the mechanical system which is neglected inthe above, and delay of the torque amplifier 3 disposed in the speedloop.

When oscillation occurs during the course of increasing Kv, therefore,the value of Kp must be again reduced, and an optimum value of Kv mustbe then searched.

As described above, in the conventional positioning servo controller, itis required to adjust an optimum gain while alternatingly changing thevalues of Kp and Kv. Unless the relationship between Kp and Kv is fullyknown, it is difficult to perform the adjustment in a well-balancedmanner.

Specifically, a skilled person knows that the controlled object in theconfiguration of FIG. 6 is a rigid body, and, when the total loadinertia of the motor and the machine is J, the state of the line (b) ofFIG. 36 can be obtained by setting Kv=4·Kp·J. However, it is difficultfor a person who has little experience and knowledge to achieve thebalance.

FIG. 37 is a control block diagram showing another conventionalpositioning servo controller which is slightly different inconfiguration from the conventional positioning servo controller of FIG.30. As shown in FIG. 37, the conventional positioning servo controlleris configured by a position controller 1, a speed controller 2, a motor4, and a differentiator 5.

The conventional positioning servo controller controls the position θ[rad] of the motor 4 in which the inertia is J [N·m·s²].

Usually, a torque amplifier which receives a produced torque command andgenerates a torque to drive the motor 4 is disposed. However, it isassumed that the response of the torque amplifier is so fast as to benegligible, and hence the torque amplifier is not shown in the figure.

For the sake of simplicity of description, it is assumed that thecontrolled object is a rigid body and the total inertia of thecontrolled object and the motor 4 is J.

The motor 4 is provided with an encoder (not shown), so that theposition θ of the motor 4 can be detected by the encoder. A positiondeviation between a position command θr which is supplied from a hostapparatus (not shown), and the position θ of the motor 4 is input to theposition controller 1 and the differentiator 5.

The position controller 1 is a proportional controller which outputs avalue obtained by multiplying the deviation with a proportional gain Kp[N·m·s²].

The differentiator 5 outputs a value which is obtained bydifferentiating the position deviation between the position command θrand the position θ of the motor 4.

The speed controller 2 is a proportional controller which outputs avalue obtained by multiplying the value obtained by the differentiator5, with a differential gain Kd [1/s] The conventional positioning servocontroller is used for causing the position θ of the motor 4 to followthe position command θr. The position θ of the motor 4 is a positionresponse with respect to the position command θr.

The torque for controlling the motor 4 in the conventional positioningservo controller is produced by the torque amplifier which is not shown,by using as the torque command a value obtained by adding together thevalues output from the position controller 1 and the speed controller 2.

FIG. 38 shows another conventional positioning servo controller whichfurther comprises an integrator 6 and an integration controller 3 inaddition to the conventional positioning servo controller shown in FIG.37.

The integrator 6 integrates the position deviation between the positioncommand θr and the position of the motor 4, and outputs the value of theintegration. The integration controller 3 amplifies the value obtainedby the integrator 3 by an integral gain Ki, and outputs the amplifiedvalue.

The torque for controlling the motor 4 in the conventional positioningservo controller is produced by the torque amplifier which is not shown,by using as the torque command a value obtained by adding together thevalues output from the position controller 1, the speed controller 2,and the integration controller 3.

In the conventional positioning servo controllers shown in FIGS. 37 and38, in order to enable the response of θ with respect to the positioncommand θr, that of θ with respect to a disturbance Td, and the like toexert a desired performance, it is necessary to adjust the values of thegains Kp, Kd, and Ki to optimum values.

In the case where the controlled object (the total of the actuator andthe machine coupled to the actuator) is an ideal rigid body, theadjustment can be easily obtained according to a control theory. In anactual controlled object, however, friction and spring elements exist,and hence the adjustment is usually conducted by cut and try.

Therefore, the parameter adjustment is a cumbersome work.

FIGS. 39 and 40 show conventional positioning servo controllers forsolving the problem.

In FIG. 39, amplifiers 27 and 28 are added to the conventionalpositioning servo controller shown in FIG. 37, and, in FIG. 40,amplifiers 27, 28, and 29 are added to the conventional positioningservo controller shown in FIG. 38.

The amplifier 27 amplifies the value output from the position controller1 by a value Kg² which is obtained by squaring an adjustment gain Kg,and outputs the amplified value.

The amplifier 28 amplifies the value output from the speed controller 8by the adjustment gain Kg, and outputs the amplified value.

The amplifier 29 amplifies the value output from the integrationcontroller 3 by a value Kg3 which is obtained by cubing the adjustmentgain Kg, and outputs the amplified value.

In the conventional positioning servo controller, the parameter Kg forsimultaneously changing a proportional element, a differential element,and an integral element is introduced, and, when the proportional gainKp, the differential gain Kd, and the integral gain Ki are oncedetermined, the gain adjustment can be conducted while achieving thebalance, simply by changing the adjustment gain Kg which is oneparameter. Therefore, it is possible to easily realize a requestedresponse characteristic.

In the conventional positioning servo controllers shown in FIGS. 39 and40, however, there arises a problem in the case where the disturbanceresponse is taken into consideration.

In the conventional positioning servo controller shown in FIG. 40, forexample, the command response which is a response of a positiondeviation θ1 with respect to the position command θr, and thedisturbance response which is a response of a position deviation θ2 withrespect to the disturbance Td are calculated as shown in FIG. 41.

In this control system, even when Kp, Kd, Ki, and Kg are adjusted so asto reduce the position deviation θ2 caused by the influence of thedisturbance Td, also the position deviation θ1 in the command responseis changed together with the position deviation θ2 in the disturbanceresponse because also the transfer function from the position command θrto the position deviation θ1 depends on only the same parameters.

Namely, such a configuration is a so-called one-degree of freedomcontrol system, and hence the adjustment cannot be adequately conductedby using only the adjustment gain Kg on the feedback side.

As a method of eliminating servo delay, there is a method in which, asin a positioning servo controller which is shown in FIG. 1 and describedlater, a speed feedforward controller 6, an acceleration feedforwardcontroller 7, and an acceleration controller 8 that performs anacceleration feedback control on the basis of the deviation between theacceleration of the motor 4 and an acceleration command to output thetorque command to the torque amplifier 3 are added.

On the other hand, as a method in which optimum adjustment of thepositioning state of the position response θ is easily conducted byadjusting various parameters of the control system such as the positionloop gain Kp and the speed loop gain Kv, there is a method in which, asin a positioning servo controller which is shown in FIG. 5 and describedlater, an amplifier 10 that multiplies an input with the adjustment gainKg is disposed behind the position controller 1 and the speed controller2.

In such a positioning servo controller, however, the adjustment gain andthe feedforward gain are adjusted by try and error to conduct optimumadjustment of the positioning state, and hence there is a problem inthat the adjustment requires a prolonged time period.

As described above, in the conventional positioning servo controllershown in FIG. 30, when physical quantities of the motor which affect thecontrol are unknown, the values of control parameters such as afeedforward gain cannot be set to optimum values, thereby producing aproblem in that an overshoot or an undershoot occurs in a controlresponse and a satisfactory control response cannot be obtained.

It is a first object of the invention to provide a positioning servocontroller in which, even when physical quantities of a motor areunknown, a satisfactory control response can be obtained.

In the conventional positioning servo controller described above, thetwo parameters must be adjusted, and hence there is a problem in that itis difficult to easily realize a requested response characteristic.

It is a second object of the invention to provide a positioning servocontroller in which a requested response characteristic can be easilyrealized.

The conventional positioning servo controller of FIG. 37 described abovehas a problem in that, even when the adjustment gain is used in order toadjust the gain of the feedback control system by one parameter, it isdifficult to easily realize a requested response characteristic in thecase of adjustment of the disturbance response.

It is a third object of the invention to provide a positioning servocontroller in which a requested response characteristic can be easilyrealized even in the case of adjustment of the disturbance response.

It is a fourth object of the invention to provide a positioning servocontroller in which optimum adjustment of the positioning state can beeasily conducted.

DISCLOSURE OF THE INVENTION

In order to attain the first object, a positioning servo controlleraccording to an embodiment of a first invention comprises: a positioncontrolling section which amplifies a position deviation between aposition command issued from a higher-level unit and a position of acontrolled object by a position loop gain, and which outputs theamplified deviation; a speed feedforward section which sets a value thatis obtained by adding a first feedforward compensation amount to thevalue output from the position controlling section, as a speed command,the first feedforward compensation amount being obtained by amplifying adifferential value of the position command by a first feedforward gain;a speed controlling section which amplifies a speed deviation betweenthe speed command and a speed of the controlled object by a speed loopgain, and which outputs the amplified deviation; an accelerationfeedforward section which sets a value that is obtained by adding asecond feedforward compensation amount to the value output from thespeed controlling section, as an acceleration command, the secondfeedforward compensation amount being obtained by amplifying adifferential value of the first feedforward compensation amount by asecond feedforward gain; an acceleration controlling section whichamplifies an acceleration deviation between the acceleration command andan acceleration of the controlled object by an acceleration loop gain,and which outputs the amplified deviation as a torque command; and atorque amplifier which drives the controlled object on the basis of thetorque command.

As described above, the positioning servo controller of the embodimentcomprises the acceleration controlling section which outputs the valueobtained by amplifying the acceleration deviation between theacceleration command and the acceleration of the controlled object bythe acceleration loop gain, as the torque command. Even when a physicalquantity of the controlled object contained in a coefficient of atransfer function in which the position command is an input and theposition response is an output is unknown, therefore, the value of theacceleration loop gain in the coefficient is a denominator of thephysical quantity of the controlled object, and an influence of thevalue of the physical quantity of the controlled object on the positionresponse can be made negligible by setting the value of the accelerationloop gain to an adequate one. Consequently, a satisfactory controlresponse can be obtained by setting the acceleration loop gain to anadequate value.

In order to attain the second object, a positioning servo controlleraccording to an embodiment of a second invention comprises: a positioncontrolling section which amplifies a position deviation between aposition command issued from a higher-level unit and a position of acontrolled object by a position loop gain, and which outputs theamplified deviation; a first amplifying section which amplifies thevalue output from the position controlling section by an adjustmentgain, and which outputs the amplified value as a speed command; adifferentiating section which differentiates the position of thecontrolled object to obtain a speed of the controlled object; a speedcontrolling section which amplifies a speed deviation between the speedcommand and the speed of the controlled object obtained by thedifferentiating section, by a speed loop gain, and which outputs theamplified deviation; a second amplifying section which amplifies thevalue output from the speed controlling section by the adjustment gain,and which outputs the amplified value as a torque command; and a torqueamplifier which drives the controlled object on the basis of the torquecommand.

As described above, in the positioning servo controller of theembodiment, when the speed loop gain and the position loop gain are onceset to determine the amount of overshoot, only the time direction ischanged by the adjustment gain. Therefore, it is possible to easilyrealize a requested response characteristic.

Another positioning servo controller according to another embodimentcomprises: a position controlling section which amplifies a positiondeviation between a position command issued from a higher-level unit anda position of a controlled object by a position loop gain, and whichoutputs the amplified deviation; a first amplifying section whichamplifies the value output from the position controlling section by anadjustment gain, and which outputs the amplified value as a speedcommand; a differentiating section which differentiates the position ofthe controlled object to obtain a speed of the controlled object; anintegrating section which integrates a speed deviation between the speedcommand and the speed of the controlled object that is obtained by thedifferentiating section, and which outputs a value that is obtained bymultiplying an integral value with a speed loop integral gain; a secondamplifying section which amplifies the value output from the integratingsection by the adjustment gain, and which outputs the amplified value; aspeed controlling section which amplifies a value that is obtained byadding the value output from the second amplifying section to a speeddeviation between the speed command and the speed of the controlledobject obtained by the differentiating section, by a speed loop gain,and which outputs the amplified deviation; a third amplifying sectionwhich amplifies the value output from the speed controlling section bythe adjustment gain, and which outputs the amplified value as a torquecommand; and a torque amplifier which drives the controlled object onthe basis of the torque command.

In the positioning servo controller, the invention is applied to apositioning servo controller in which the position is controlled by theP (Proportional) control and the speed is controlled by the P-I(Proportional-Integral) control.

A positioning servo controller of a further embodiment comprises: aposition controlling section which amplifies a position deviationbetween a position command issued from a higher-level unit and aposition of a controlled object by a position loop gain, and whichoutputs the amplified deviation; a first amplifying section whichamplifies the value output from the position controlling section by anadjustment gain, and which outputs the amplified value as a speedcommand; a differentiating section which differentiates the position ofthe controlled object to obtain a speed of the controlled object; anintegrating section which integrates a speed deviation between the speedcommand and the speed of the controlled object that is obtained by thedifferentiating section, and which outputs a value that is obtained bymultiplying an integral value with a speed loop integral gain; a secondamplifying section which amplifies the value output from the integratingsection by the adjustment gain, and which outputs the amplified value; aspeed controlling section which amplifies a deviation between the valueoutput from the second amplifying section and the speed of thecontrolled object by a speed loop gain, and which outputs the amplifieddeviation; a third amplifying section which amplifies the value outputfrom the speed controlling section by the adjustment gain, and whichoutputs the amplified value as a torque command; and a torque amplifierwhich drives the controlled object on the basis of the torque command.

In the positioning servo controller, the invention is applied to apositioning servo controller in which the position is controlled by theP (Proportional) control and the speed is controlled by the I-P(Integral-Proportional) control.

In order to attain the third object, a positioning servo controlleraccording to an embodiment of a third invention comprises: a positioncontrolling section which amplifies a position deviation between aposition command issued from a higher-level unit and a position of acontrolled object, by a proportional gain, and which outputs theamplified deviation; a first amplifying section which amplifies thevalue output from the position controlling section by a value that isobtained by squaring an adjustment gain, and which outputs the amplifiedvalue; a differentiating section which differentiates the positiondeviation between the position command and the controlled object; aspeed controlling section which amplifies a value obtained by thedifferentiating section, by a differential gain, and which outputs theamplified value; a second amplifying section which amplifies the valueoutput from the speed controlling section by the adjustment gain, andwhich outputs the amplified value; a feedforward controlling sectionwhich outputs a value that is obtained by adding a value obtained byamplifying a value obtained by second-order differentiation of theposition command, by a first feedforward gain, to a value obtained byamplifying a value obtained by differentiating the position command, bya second feedforward gain and the adjustment gain; and a torqueamplifier which sets a value obtained by adding together the valuesoutput from the first and second amplifying sections and the feedforwardsection, as a torque command, and which drives the controlled object onthe basis of the torque command.

As described above, according to the third invention, the feedforwardcontrolling section is disposed to set the control system as atwo-degree of freedom system, and the gain of the feedforwardcontrolling section and that of the feedback system can be adjusted bythe adjustment gain which is one parameter. Therefore, the gainadjustment for determining the requested response characteristic can besimplified.

In another embodiment, in addition to the above configuration, thecontroller may further comprise: an integrating section which integratesthe position deviation between the position command and the position ofthe controlled object; an integration controlling section whichamplifies a value obtained by the integrating section, by an integralgain, and which outputs the amplified value; and a third amplifyingsection which amplifies the value output from the integrationcontrolling section, by a value that is obtained by cubing theadjustment gain, and which outputs the amplified value.

In a further embodiment, in addition to the above configuration, thecontroller may further comprise: a second-order differentiating sectionwhich performs second-order differentiation on the position deviationbetween the position command and the controlled object; and anacceleration controlling section which amplifies a value obtained by thesecond-order differentiating section, by an acceleration gain, and whichoutputs the amplified value.

In order to attain the fourth object, an embodiment of a fourthinvention comprises: a position controlling section which amplifies aposition deviation between a position command issued from a higher-levelunit and a position of a controlled object, by a position loop gain, andwhich outputs the amplified deviation; a first amplifying section whichamplifies the value output from the position controlling section by anadjustment gain, and which outputs the amplified value; a speedfeedforward controlling section which sets a value that is obtained byadding a first feedforward compensation amount to the value output fromthe first amplifying section, as a speed command, the first feedforwardcompensation amount being obtained by amplifying a differential value ofthe position command by a first feedforward gain; a speed controllingsection which amplifies a speed deviation between the speed command anda speed of the controlled object by a speed loop gain, and which outputsthe amplified deviation; a second amplifying section which amplifies thevalue output from the speed controlling section by the adjustment gain,and which outputs the amplified value; an acceleration feedforwardsection which sets a value that is obtained by adding a secondfeedforward compensation amount to the value output from the secondamplifying section, as an acceleration command, the second feedforwardcompensation amount being obtained by amplifying a differential value ofthe first feedforward compensation amount by a second feedforward gain;an acceleration controlling section which amplifies an accelerationdeviation between the acceleration command and an acceleration of thecontrolled object by an acceleration loop gain, and which outputs theamplified deviation as a torque command; and a torque amplifier whichdrives the controlled object on the basis of the torque command, valuesof the first feedforward gain and the second feedforward gain beingvalues of functions in which a value of the adjustment gain is used asan argument.

In the positioning servo controller of the fourth invention, the valuesof the first feedforward gain and the second feedforward gain are thoseof functions in which the adjustment gain is used as an argument,thereby enabling optimization of the positioning state to be conductedsimply by adjusting the adjustment gain. Therefore, optimum adjustmentof the positioning state can be easily conducted.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a control block diagram showing the configuration of apositioning servo controller of a first embodiment.

FIG. 2 is a simplified control block diagram of the control blockdiagram of FIG. 1.

FIG. 3 is a simplified control block diagram of the control blockdiagram of FIG. 2.

FIGS. 4(a) and 4(b) are graphs showing the operation of a positioningservo controller of an embodiment of the invention.

FIG. 5 is a block diagram showing the configuration of a firstpositioning servo controller of a second embodiment.

FIG. 6 is a pole map illustrating the operation of the positioning servocontroller of FIG. 5.

FIG. 7 is a view showing changes of the response characteristic in thecase where the value of an adjustment gain Kg is changed.

FIG. 8 is a block diagram showing the configuration of a secondpositioning servo controller of the second embodiment.

FIG. 9 is a block diagram showing the configuration of a thirdpositioning servo controller of a third embodiment.

FIG. 10 is a block diagram showing the configuration of a firstpositioning servo controller of the third embodiment.

FIG. 11 is a view illustrating a response of the positioning servocontroller of FIG. 10.

FIG. 12 is a pole map illustrating the operation of a disturbanceresponse in the positioning servo controller of FIG. 10.

FIG. 13 is a pole map illustrating the operation of a command responsein the positioning servo controller of FIG. 10.

FIG. 14 is a view showing changes of response waveforms in the casewhere the value of the adjustment gain Kg is changed in the positioningservo controller of FIG. 10.

FIG. 15 is a view showing changes of the response waveforms in the casewhere feedforward gains Kff1 and kff2 are set to 0.

FIG. 16 is a view showing changes of the response waveforms in the casewhere the adjustment gain Kg in a feedforward controller 10 is set to 1.

FIG. 17 is a block diagram showing the configuration of a secondpositioning servo controller of the third embodiment.

FIG. 18 is a view illustrating a response of the positioning servocontroller of FIG. 17.

FIG. 19 is a block diagram showing the configuration of the thirdpositioning servo controller of the third embodiment.

FIG. 20 is a view illustrating a response of the positioning servocontroller of FIG. 19.

FIG. 21 is a control block diagram showing the configuration of apositioning servo controller of the feedforward control system in whicha conventional adjustment gain is used.

FIGS. 22(a) to 22(d) is an equivalent block diagram of the control blockdiagram of FIG. 21.

FIGS. 23(a) and 23(b) are the block diagrams showing the configurationof the positioning servo controller of FIG. 21 including a mechanicalsystem which is a controlled object.

FIG. 24 is a graph showing variations of a position command and aposition response in the case where the mechanical system has highrigidity.

FIG. 25 is a graph showing variations of the position command and theposition response in the case where the mechanical system has lowrigidity.

FIG. 26 is a graph showing variations of the position command and theposition response in the case where the value of the adjustment gain isadjusted.

FIG. 27 is a graph showing variations of the position command and theposition response in the case where a feedforward gain is adjusted.

FIG. 28 is a graph showing variations of the position command and theposition response in the case where optimum adjustment of thepositioning state is conducted.

FIGS. 29(a) and 29(b) are the control block diagrams showing theconfiguration of a positioning servo controller of a fourth embodiment.

FIG. 30 is a control block diagram showing the configuration of aconventional positioning servo controller.

FIGS. 31(a) and 31(b) are the graphes showing the operation of theconventional positioning servo controller.

FIG. 32 is a control block diagram showing the configuration of apositioning servo controller in which the feedforward control system isused together with the feedback control system.

FIG. 33 is a simplified control block diagram of the control blockdiagram of FIG. 32.

FIG. 34 is a simplified control block diagram of the control blockdiagram of FIG. 33.

FIGS. 35(a) and 35(b) show the graphs for the operation of theconventional positioning servo controller.

FIG. 36 is a view showing changes of a response characteristic of theconventional positioning servo controller.

FIG. 37 is a block diagram showing the configuration of the conventionalpositioning servo controller.

FIG. 38 is a block diagram showing the configuration of anotherconventional positioning servo controller.

FIG. 39 is a block diagram showing the configuration of a positioningservo controller in which the conventional positioning servo controllerof FIG. 37 is modified so that a gain adjustment is performed by anadjustment gain Kg.

FIG. 40 is a block diagram showing the configuration of a positioningservo controller in which the conventional positioning servo controllerof FIG. 38 is modified so that a gain adjustment is performed by anadjustment gain Kg.

FIG. 41 is a view illustrating a response of the positioning servocontroller of FIG. 40.

In the figures, the reference numeral 1 denotes a position controller, 2denotes a speed controller, 3 denotes a torque amplifier, 4 denotes amotor, 5 and 9 denote differentiators, 6, 7, 10, 11, 22, and 23 denotefeedforward controllers, 8 denotes an acceleration controller, 12denotes a second-order differentiator, 13 denotes an accelerationcontroller, 16 denotes an integrator, 17 denotes a differentiator, 27,28, and 29 denote amplifiers, and 30 denotes a controlled object.

BEST MODE FOR CARRYING OUT THE INVENTION

Next, embodiments of the inventions will be described with reference tothe drawings.

In all the figures, all components which are denoted by the samereference numeral indicate the identical member.

(Embodiment 1)

First, a positioning servo controller of Embodiment 1 of the inventionwhich attains the first object will be described in detail withreference to FIGS. 1 to 4.

FIG. 1 is a control block diagram showing the configuration of apositioning servo controller of the one embodiment. The positioningservo controller of the embodiment is different from the conventionalpositioning servo controller of FIG. 32, in that the controllercomprises an acceleration controller 8 and a differentiator 9.

The differentiator 9 performs second-order differentiation on theposition response θ of the motor 4 to output the acceleration of themotor 4. The acceleration controller 8 is a proportional controllerwhich receives an acceleration deviation between the value that isobtained by adding together the value output from the speed controller 2and that output from the feedforward controller 7, and the accelerationof the motor 4 that is output from the differentiator 9, and whichoutputs a value that is obtained by multiplying the accelerationdeviation with an acceleration loop gain Ka, as the torque command Tr tothe torque amplifier 3.

FIG. 2 shows a simplified diagram of the control block diagram of FIG.1.

In order to further simplify the control block diagram of FIG. 2, it isassumed that the feedforward gain Kff1=1. Then, the control blockdiagram of FIG. 2 is simplified as shown in a control block diagram ofFIG. 3.

When the control block diagram of FIG. 3 is compared with that of FIG.34, the coefficient of the term of S² in the denominator is J in thecontrol block diagram of FIG. 34, and by contrast it is 1+J/Ka in thecontrol block diagram of FIG. 3.

In the transfer function G, the value of the acceleration loop gain Kais the denominator of the inertia J of the motor 4. As the value of theacceleration loop gain Ka is larger, therefore, J/Ka becomes nearer to0.

Namely, even when the value of the inertia J is not clearly known, theinfluence of the inertia J on the position response θ can be reduced bysetting the value of the acceleration loop gain Ka to an adequate one.

In the control block diagram of FIG. 3, when the feedforward gainKff2=1, the transfer function G between the position command θr and theposition response θ can be made substantially equal to 1, so that thedelay of the position response θ with respect to the position command θrcan be eliminated.

FIGS. 4(a) and 4(b) are the graphes showing the operation of thepositioning servo controller of the embodiment in the case where Kp=25[1/s], Kv=200 [1/s], Ka=10, Kff1=1 [1/s], and Kff2=1 [1/s].

FIGS. 4(a) and 4(b) show manners of variations of differentials dθ/dtand dθ/dt of the position command θr and the position response θ.

The waveform of dθr/dt in FIGS. 4(a) and 4(b) is identical with that ofdθr/dt in FIGS. 35(a) and 35(b).

In FIGS. 4(a) and 4(b), it is assumed that also the values of theacceleration/deceleration time, the steady-state speed, thepredetermined time period, the position loop gain Kp, the speed loopgain Kv, and the inertia J are equal to those in FIGS. 35(a) and 35(b),and the acceleration loop gain Ka=10 and the feedforward gains Kff1=1and Kff2=1.

When FIG. 4(b) which is an enlarged view of the portion B in FIG. 4(a)is compared with FIG. 35(b), it will be seen that the amount ofovershoot of the speed response dθ/dt is reduced.

As described above, the positioning servo controller of the embodimentcomprises the acceleration controller 8 which outputs a value that isobtained by amplifying the acceleration deviation between theacceleration command and the acceleration of the motor 4 by anacceleration loop gain Ka, as the torque command.

According to the configuration, in the positioning servo controller ofthe embodiment, even when the inertia J of the motor 4 contained in thecoefficient of the transfer function G in which the position command θris an input and the position response θ is an output is unknown, theacceleration loop gain Ka is the denominator of the inertia J of themotor 4 in the coefficient of the transfer function G, and hence aninfluence of the inertia J of the motor 4 on the position response θ canbe made negligible by setting the value of the acceleration loop gain Kato an adequate one.

In the positioning servo controller of the embodiment, therefore, asatisfactory control response can be obtained.

In the positioning servo controller of the embodiment, even when thevalue of the inertia J of the motor 4 is changed, the influence of theinertia J of the motor 4 on the position response θ can be madenegligible by setting the value of the acceleration loop gain Ka to anadequate one. Therefore, a satisfactory control response can beobtained.

In the positioning servo controller of the embodiment, when the value ofthe inertia J is clearly known, the transfer function G=1 can beattained by setting

Kff 2=1+J/Ka.

Consequently, the positioning servo controller of the embodiment canoptimumly position the motor 4 irrespective of whether the value of theinertia J is clearly known or not.

As described above, the positioning servo controller of the inventioncomprises the acceleration controller which outputs the value that isobtained by amplifying the acceleration deviation between theacceleration command and the actual acceleration of the motor by theacceleration loop gain, as the torque command. Even when the inertia ofthe motor contained in the coefficient of the transfer function in whichthe position command is an input and the position response is an outputis unknown, therefore, the value of the acceleration loop gain in thetransfer function is a denominator of the inertia of the motor.

Consequently, an influence of the inertia of the motor on the positionresponse can be made negligible by setting the value of the accelerationloop gain to an adequate one. In the positioning servo controller of theinvention, therefore, a satisfactory control response can be obtained.

(Embodiment 2)

Next, Embodiment 2 of the invention which attains the second object willbe described in detail with reference to FIGS. 5 to 9.

(Embodiment 2-1)

FIG. 5 is a block diagram showing the configuration of a positioningservo controller of Embodiment 2-1.

In FIG. 5, components identical with those of FIG. 6 are denoted by thesame reference numerals, and their description is omitted.

The positioning servo controller of the embodiment is configured sothat, in the conventional positioning servo controller shown in FIG. 6,amplifiers 101 and 102 are disposed behind the position controller 1 andthe speed controller 2, respectively.

The amplifier 101 multiplies the value output from the positioncontroller 1 with the adjustment gain Kg, and outputs the resultingvalue as the speed command ωr. The amplifier 102 multiplies the valueoutput from the speed controller 2 with the adjustment gain Kg, andoutputs the resulting value as the torque command Tr.

For the sake of simplicity of description, also in the embodiment, inthe same manner as the conventional art example, it is assumed that thecontrolled object is a rigid body and the total inertia of thecontrolled object and the motor 4 is J, and also that the response ofthe torque amplifier 3 is so fast as to be negligible.

When the transfer function G(S) from the position command θr of FIG. 5to the position response is calculated (in this case, it is assumed thatKv0=Kv/J, because the speed loop gain Kv is usually changed inconjunction with the inertia J), the follows are attained:

G(S)=G 1/G 2  (1)

G 1=Kg ² ·Kv 0 ·Kp  (2)

G 2=(S ² +Kg·Kv 0 ·S+Kg ² ·Kv 0 ·Kp)  (3)

The stability of the control system is determined by the root of thecharacteristic equation G2=0, i.e., poles ρ+ and ρ− of the controlsystem.

From expression (3)

ρ+=−Kg{Kv 0−(Kv 0 ² −Kv 0 ·Kp)0.5}/2  (4)

ρ−=−Kg{Kv 0−(Kv 0 ² +Kv 0 ·Kp)0.5}/2  (5)

Then, it is assumed that Kv0 and Kp are once determined. When Kg ischanged, only the scale relating to the time in the pole assignment ischanged, and the amount relating to overshoot is not changed.

In order to describe the above in a form which is usually used, thefollowing is set:

G 2=(S ²+2ζωS+ω ²)  (6)

Then, the followings are obtained:

ω=Kg(Kv 0 ·Kp)0.5  (7)

ζ=(Kv 0/Kp)0.5/2  (8)

From the above, it will be seen that only ω relates to Kg.

FIG. 6 shows the pole assignment in this case. It will be seen that,when Kp and Kv0 are once determined, the amount of overshoot is notchanged by Kg, and hence the balance of the response waveform is notchanged, and only the time direction (i.e., ω) is changed.

In FIG. 7, for example, Kg is changed from 0.5 to 5. The state wherethere is no overshoot is unchanged, and only the response speed isenhanced. In the figure, it is assumed that Kg=1 in the state of theline (b) of FIG. 36.

As described above, in the positioning servo controller of theembodiment, when the values of Kv and Kp are once determined and thenfixed, the response characteristic depends on the one parameter or Kg.

(Embodiment 2-2)

Next, a positioning servo controller of Embodiment 2-2 will bedescribed.

FIG. 8 is a block diagram showing the configuration of the positioningservo controller of the second embodiment of the invention.

In the positioning servo controller of the embodiment, the invention isapplied to a positioning servo controller in which the position iscontrolled by the P (Proportional) control and the speed is controlledby the P-I (Proportional-Integral) control.

The positioning servo controller of the embodiment is configured sothat, in the positioning servo controller of the first embodiment shownin FIG. 5, an integrator 16 and an amplifier 103 are further disposed.

The integrator 16 integrates the speed deviation between the speedcommand ωr and the speed ω of the motor 4, and outputs a value which isobtained by multiplying the result of the integration with the integralgain Ki. The amplifier 103 multiplies the value output from theintegrator 16 with the adjustment gain Kg, and outputs the result of themultiplication to the speed controller 2.

The speed controller 2 in the embodiment receives a value which isobtained by adding the value output from the amplifier 103 to the speeddeviation between the speed command ωr output from the amplifier 101 andthe speed ω of the motor 4 that is obtained by the differentiator 5, andoutputs a value which is obtained by multiplying the value with thespeed loop gain Kv, to the amplifier 102.

When the transfer function G(S) from the position command θr to theposition response θ is calculated, the follows are attained:

G(S)=G 1/G 2  (9)

G 1=Kg ² ·Kv 0 ·KD(S+Kg ² ·Ki)  (10)

G 2=(S ³ +Kg·Kv 0 ·S ² +Kg ²(Kv 0 ·Ki+Kv 0 ·Kp)S+Kg ³ ·Kv 0·Kp·Ki)  (11)

With respect to the root (pole) of the characteristic equation G2=0,when Kv0, Ki, and Kp are once determined, the waveform is not changed bythe value of Kg.

For example, the case where G2=0 has a triple root—Kgρ will beconsidered. Then, the following is obtained: $\begin{matrix}\begin{matrix}{{G2} = ( {S + {{Kg}\quad \rho}} )^{3}} \\{= ( {S^{3} + {3{Kg}\quad \rho \quad S^{2}} + {3{Kg}^{2}\rho^{3}S} + {{Kg}^{3}\rho^{3}}} )}\end{matrix} & (12)\end{matrix}$

When expressions (11) and (12) are compared with each other, thefollowings are attained:

Kv 0=3ρ,

3ρ² =Kv 0 ·Ki+Kv 0 ·Kp,

ρ³ =Kv 0 ·Kp·Ki  (13)

Therefore, ρ is a constant which, when Kv0, Ki, and Kp are oncedetermined, is determined irrespectively of the value of Kg.

From expression (12), therefore, the triple root—Kgρ is changed only inmagnitude when Kg is changed, and remains to be a triple root. In otherwords, the response characteristic is unchanged.

(Embodiment 2-3)

Next, a positioning servo controller of Embodiment 2-3 will bedescribed.

FIG. 9 is a block diagram showing the configuration of the positioningservo controller of the third embodiment of the invention.

In the positioning servo controller of the embodiment, the invention isapplied to a positioning servo controller in which the position iscontrolled by the P (Proportional) control and the speed is controlledby the I-P (Proportional-Integral) control.

The positioning servo controller of the embodiment is configured sothat, in the positioning servo controller of the second embodiment shownin FIG. 8, a differentiator 17 is further disposed. The differentiator17 differentiates the position θ of the motor 4, and outputs the speed ωof the motor 4.

The speed controller 2 in the embodiment receives a value which isobtained by adding the value of the speed ω that is the output of thedifferentiator 17 to the value output from the amplifier 103, andoutputs a value which is obtained by multiplying the value with thespeed loop gain Kv.

The characteristic equation of the transfer function G(S) from theposition command θr to the position response θ in the positioning servocontroller of the embodiment is as follows:

G 2′=(S ³ +Kg·Kv 0 ·S ² +Kg ² Kv 0 ·Ki·s+Kg ³ ·Kv 0 ·Kp·Ki)  (14)

When expressions (12) and (14) are compared with each other, thefollowings are attained:

Kv 0=3ρ,

3ρ² =Kv 0 ·Ki,

ρ³ =Kv 0 ·Kp·Ki  (15)

Therefore, ρ is a constant which, when Kv0, Ki, and Kp are oncedetermined, is determined irrespectively of the value of Kg.

Consequently, the positioning servo controller of the embodiment canattain the same effects as those of the positioning servo controller ofthe second embodiment.

Embodiments 2-1 to 2-3 have been described in the case where theposition loop gain Kp and the speed loop gain Kv are constants. Theinvention is not restricted to such a case, and is effective also in thecase where the position loop gain Kp and the speed loop gain Kv can bechanged by internal variables such as the position deviation, thefeedback speed, and the like, and facilitates adjustment of parameters.

In such a case, namely, it is required to make only Kg variable whilemaintaining the position loop gain Kp, the speed loop gain Kv, and thespeed loop integral gain Ki to be fixed.

As described above, according to the invention, the responsecharacteristic can be adjusted simply by adjusting one parameter, andhence the effect that a requested response characteristic can be easilyrealized is attained.

(Embodiment 3)

Next, Embodiment 3 of the invention which attains the third object willbe described in detail with reference to FIGS. 10 to 20.

(Embodiment 3-1)

FIG. 10 is a block diagram showing the configuration of a positioningservo controller of Embodiment 3-1.

In FIG. 10, components identical with those of FIG. 39 are denoted bythe same reference numerals, and their description is omitted.

The positioning servo controller of the embodiment is configured sothat, in the conventional positioning servo controller shown in FIG. 39,a feedforward controller 10 is further disposed to set the controlsystem as a two-degree of freedom system, and the gain is correlatedwith the adjustment gain Kg which is a common parameter of the feedbacksystem.

The feedforward controller 10 outputs a value that is obtained by addinga value obtained by amplifying a value obtained by second-orderdifferentiation of the position command θr, by the feedforward gainKff1, to a value obtained by amplifying a value obtained by first-orderdifferentiation of the position command θr, by the feedforward gain Kff2and the adjustment gain Kg.

In the embodiment, the torque for controlling the motor 4 is produced bya torque amplifier which is not shown, by using a value obtained byadding together the values output from the amplifiers 27 and 28 and thefeedforward controller 10, as the torque command.

FIG. 11 shows the transfer function of the positioning servo controllerof the embodiment shown in FIG. 10. At this time, the disturbanceresponse depends only on the denominator of the transfer function fromthe disturbance Td to θ2.

When this is indicated by Gd, this is expressed by expression (16)below.

For the sake of simplicity of description, it is assumed that J=1.

Gd=S ² +Kg·Kd·S+Kg ² ·Kp  (16)

The stability of the control system is determined by the root of thecharacteristic equation Gd=0, i.e., poles ρ+ and ρ− of the controlsystem.

From expression (16)

ρ+=−Kg{Kd−(Kd ²−4Kp)^(0.5)}/2  (17)

ρ−=−Kg{Kd+(Kd ²−4Kp)^(0.5)}/2  (18)

Then, it is assumed that Kd and Kp are once determined. When Kg ischanged, only the scale relating to the time in the pole assignment ischanged, and the amount relating to overshoot is not changed.

In order to describe the above in a form which is usually used, thefollowing is set:

Gd=(S ²+2ζωS+ω ²)  (19)

Then, the followings are obtained:

ω=Kg(Kp)^(0.5)  (20)

ζ=Kd/(2Kp ^(0.5))  (21)

From the above, it will be seen that only ω relates to Kg.

FIG. 12 shows the pole assignment in this case. It will be seen that,when Kp and Kd are once determined, the amount of overshoot is notchanged by Kg, and hence the balance of the response waveform is notchanged, and only the time direction (i.e., ω) is changed.

On the other hand, the command response is determined by the transferfunction from the position command θr to the position deviation θ1. Thetransfer function in this case is set as G=G1/G2. In addition to thedenominator, also the numerator is changed by the control gain.Therefore, the responsibility of the control system is determined by theroot of the characteristic equation G2=0, i.e., poles ρ+ and ρ− of thecontrol system, and the root of the characteristic equation G1=0, i.e.,the zero point of the control system.

With respect to the poles, since G2=Gd, expressions (16) to (21) aresimilarly applicable as they are. Consequently, only the zero point willbe discussed here. For the sake of simplicity of description, it isassumed that J=1.

The following is set:

G 1 =Kff 1 ·S ² +Kg(Kd+Kff ₂)S+Kg ² ·Kp=0  (22)

By solving this expression (22), zero points z+ and z− are determined.

From expression (22), following expressions (23) and (24) are obtained:

z ₊ =−Kg{Kd+Kff 2}−[(Kd+Kff 2)²−4Kff 1 ·Kp] ^(0.5)}/(2Kff 1)  (23)

z−=−Kg{Kd+Kff 2}+[(Kd+Kff 2)²−4Kff 1 ·Kp] ^(0.5)}/(2Kff 1)  (24)

Even if Kd and Kp which determine the poles are once determined, theresponse can be changed by Kff1 and Kff2.

Namely, the control system can be determined independently of thedisturbance response.

By contrast, when Kd, Kp, Kff1, and Kff2 are once determined, only thescale relating to the time is changed by Kg, and the amount relating toovershoot is not changed.

In order to describe the above in a form which is usually used, thefollowing is set:

G 1 =Kff 1(S ²+2ζ1ω1S+ω1²)  (25)

Then, the followings are obtained:

 ω1=Kg(Kp/kff 1)^(0.5)  (26)

ζ1=(Kd+Kff 2)/{2(Kff 1 ·Kp)^(0.5)}  (27)

From the above, it will be seen that only ω1 relates to Kg.

FIG. 13 shows the pole assignment in this case. It will be seen that,when Kd, Kp, Kff1, and Kff2 are once determined, the balance is notchanged by Kg, and only the time direction (i.e., ω1) is changed.

FIG. 14 shows the response waveform in the embodiment.

FIG. 14 shows the response waveform in the case where Kg is changed from0.5 to 1.5. The whole waveform is not changed, and only the responsespeed is enhanced.

In this case, Kd=40, Kp=800, Kff1=0, Kff2=−16, and J=1, and the positioncommand θr is set so that the maximum speed=200 (rad/s), theacceleration time and the deceleration time=0.05 (sec), and the commanddelivery time is 0.1 (sec).

In this way, after Kd and Kp are once determined, with respect to thecommand response, the response characteristic is determined by the oneparameter or Kg.

FIG. 15 shows response waveforms in the embodiment in the case where, inorder to compare the effect of the positioning servo controller of theembodiment with that of the conventional art example, the feedforwardgain Kff1=Kff2=0 and Kg is changed from 0.5 to 1.5. By settingKff1=Kff2=0, the response waveforms of FIG. 15 become those of theconventional positioning servo controller shown in FIG. 39.

When the response waveforms of FIG. 15 which are the response waveformsof the conventional positioning servo controller in which thefeedforward controller 10 is not disposed is compared with those shownin FIG. 14, it will be seen that the response waveforms in theconventional positioning servo controller are larger in amount ofovershoot.

In the positioning servo controller of the embodiment, the gain of thefeedforward controller 10 is correlated with the adjustment gain Kgwhich is a common parameter of the feedback system, thereby enabling theresponse characteristic to be adjusted by one parameter, i.e., theadjustment gain Kg.

In other words, in the case where a feedforward controller is simplydisposed in a conventional positioning servo controller and theadjustment gain Kg is not contained in the gain of the feedforwardcontroller, it is difficult to adjust the response characteristic, andthe effect of the embodiment cannot be attained.

In order to describe the above, FIG. 16 shows response waveforms in thecase where Kg of the feedforward controller 10 of FIG. 10 is set to 1and Kg is changed from 0.5 to 1.5.

Referring to FIG. 16, it will be seen that, with respect to the commandresponse, the waveform is largely changed in accordance with theadjustment gain Kg and hence adjustment is difficult.

In the positioning servo controller of the embodiment, the feedforwardgains Kff1 and Kff2 can be set independent of the feedback controlsystem, and, in both the feedback and feedforward control systems, Kg²is multiplied with the position term, and Kg is multiplied with thespeed term (first-order differential term). When the response waveformis once determined, therefore, it is required only to adjust theadjustment gain Kg, thereby enabling only the operation time to bechanged while maintaining the response waveform.

In the positioning servo controller of the embodiment, namely, thefeedforward controller 10 is disposed to set the control system as atwo-degree of freedom system, and the gain of the feedforward controller10 and that of the feedback system can be adjusted by the adjustmentgain Kg which is one parameter. Therefore, the gain adjustment fordetermining the requested response characteristic can be simplified.

(Embodiment 3-2)

Next, a positioning servo controller of Embodiment 3-2 will bedescribed.

FIG. 17 is a block diagram showing the configuration of a positioningservo controller of the second embodiment of the invention, and FIG. 18is a view illustrating the response of the positioning servo controllerof FIG. 17.

The positioning servo controller of the embodiment is configured sothat, in the conventional positioning servo controller shown in FIG. 40,a feedforward controller 11 is further disposed.

The feedforward controller 11 outputs a value that is obtained by addingtogether a value obtained by amplifying a value obtained by second-orderdifferentiation of the position command θr, by the feedforward gainKff1, a value obtained by amplifying a value obtained by differentiatingthe position command θr, by the feedforward gain Kff2 and the adjustmentgain Kg, and a value obtained by amplifying the position command θr by afeedforward gain Kff3 and Kg² which is a square of the adjustment gainKg.

In the embodiment, the torque for controlling the motor 4 is produced bya torque amplifier which is not shown, by using a value obtained byadding together the values output from the amplifiers 27, 28, and 29 andthe feedforward controller 11, as the torque command.

In the positioning servo controller of the embodiment, the feedforwardcontroller 11 is disposed to set the control system as a two-degree offreedom system, and the gain of the feedforward controller 11 and thatof the feedback system can be adjusted by the adjustment gain Kg whichis one parameter. In the same manner as the positioning servo controllerof the first embodiment, therefore, the gain adjustment for determiningthe requested response characteristic can be simplified.

(Embodiment 3-3)

Next, a positioning servo controller of Embodiment 3-3 will bedescribed.

FIG. 19 is a block diagram showing the configuration of a positioningservo controller of the third embodiment of the invention, and FIG. 20is a view illustrating the response of the positioning servo controllerof FIG. 19.

The positioning servo controller of the embodiment is configured sothat, in the positioning servo controller of the third embodiment shownin FIG. 17, a second-order differentiator 12 and an accelerationcontroller 13 are further disposed.

The second-order differentiator 12 performs second-order differentiationon the position deviation between the position command θr and thecontrolled object. The acceleration controller 13 outputs a value thatis obtained by amplifying the value obtained by the second-orderdifferentiator 12, by an acceleration gain Ki.

In the embodiment, the torque for controlling the motor 4 is produced bya torque amplifier which is not shown, by using a value obtained byadding together the values output from the amplifiers 27, 28, and 29,the acceleration controller 13, and the feedforward controller 11, asthe torque command.

In the positioning servo controller of the embodiment, the feedforwardcontroller 11 is disposed to set the control system as a two-degree offreedom system, and the gain of the feedforward controller 11 and thatof the feedback system can be adjusted by the adjustment gain Kg whichis one parameter. In the same manner as the positioning servo controllerof the first embodiment, therefore, the gain adjustment for determiningthe requested response characteristic can be simplified.

As described above, according to the invention, both the gains of thefeedback and feedforward control systems can be adjusted simply byadjusting one parameter, to adjust the response waveform, and hence itis possible to attain an effect that a requested response characteristiccan be easily realized even in the case of adjustment of the disturbanceresponse.

(Embodiment 4)

Next, an embodiment of the fourth invention which is an improvement ofthe above-mentioned first and second inventions will be described withreference to FIGS. 21 to 29.

As described above, in a positioning servo controller, usually, a speedloop process is disposed as a minor loop in the position loop process.In such a positioning servo controller of the feedback control system,the values of the position loop gain Kp and the speed loop gain Kv arefinite values and have the upper limit. Therefore, the position responseθ of the motor 4 fails to completely coincide with the position commandθr, and so-called servo delay occurs.

As a method of eliminating such servo delay, there is a method in which,as in the above-mentioned positioning servo controller which is shown inFIG. 1, the speed feedforward controller 6, the acceleration feedforwardcontroller 7, and the acceleration controller 8 that performs anacceleration feedback control on the basis of the deviation between theacceleration of the motor 4 and the acceleration command to output thetorque command to the torque amplifier 3 are added.

The speed feedforward controller 6 outputs a first feedforwardcompensation amount which is obtained by amplifying a differential valueof the position command θr by the feedforward gain Kff1 that is a firstfeedforward gain.

The first feedforward compensation amount is added to the value outputfrom the position controller 1.

The acceleration feedforward controller 7 outputs a second feedforwardcompensation amount which is obtained by amplifying a differential valueof the first feedforward compensation amount by the feedforward gainKff2 that is a second feedforward gain.

The second feedforward compensation amount is added to the value outputfrom the speed controller 2.

In the positioning servo controller of FIG. 1, even in the case wherethe inertia J of the motor 4 is not clearly known, when the value of theacceleration loop gain Ka of the acceleration controller 8 is set to anadequate one, the influence of the inertia J on the control response ofthe positioning servo controller can be eliminated. When theacceleration feedforward gain Kff2=1, the transfer function in which theposition command θr is an input and the position response θ is an outputis set to 1, whereby servo delay can be eliminated.

On the other hand, as a method in which optimum adjustment of thepositioning state of the position response θ is easily conducted byadjusting various parameters of the control system such as the positionloop gain Kp and the speed loop gain Kv, there is a method in which, asin the above-mentioned positioning servo controller which is shown inFIG. 5, the amplifier 10 that multiplies an input with the adjustmentgain Kg is disposed behind the position controller 1 and the speedcontroller 2.

In this positioning servo controller, optimum adjustment of thepositioning state of the position response θ can be easily conducted byadjusting only the adjustment gain Kg and without separately adjustingthe position loop gain Kp and the speed loop gain Kv.

FIG. 21 is a control block diagram showing the configuration of apositioning servo controller in which the above-mentioned two methodsare used.

In such a positioning servo controller, as described above, servo delaycan be eliminated, and optimum adjustment of the positioning state canbe easily conducted.

The block diagram of the positioning servo controller of FIG. 21 can bemodified as shown in FIGS. 22(a) and 22(b). In this case, it is assumedthat the torque amplifier has a gain of 1.

Usually, a mechanical system which is a controlled object of thepositioning servo controller is coupled to the shaft end of the motor 4of the controller.

In the case where the value of the gain of a feedback control system,such as the adjustment gain Kg can be largely increased, usually, themechanical system can be deemed as a rigid member of a highcharacteristic frequency.

In the case where the value of the gain of a feedback control system,such as the adjustment gain Kg cannot be largely increased, themechanical system can be deemed as a mechanical system of low rigidityand a low characteristic frequency.

In the case where the mechanical system can be deemed as a rigid memberof a high characteristic frequency, the feedforward gains Kff1 and Kff2can be set to 1, and the block diagram of FIG. 22(b) can be replacedwith that of FIG. 22(c).

When the value of the acceleration loop gain Ka is set to besufficiently larger than that of the inertia J, J/Ka can be deemed to 0,and hence the block diagram of FIG. 22(c) can be replaced with that ofFIG. 22(d).

FIG. 23(a) is a block diagram of the positioning servo controllerincluding a mechanical system which is a controlled object. In FIG.23(a), it is assumed that the reaction force from a mechanical system 11to the motor 4 is so small as to be negligible.

In the figure, θM denotes the position of the motor, θL denotes theposition response θ of the mechanical system 11 coupled to the motor 4,ω denotes the resonance frequency of the mechanical system 11, and ζdenotes the damping coefficient of the mechanical system 11.

When the inertia of the mechanical system 11 is indicated by JL and thespring constant by K, ω has the following value:

ω=(K/JL)^(0.5).

In the case where the mechanical system 11 is an oscillation system, ζis smaller than 1.

If the feedforward gains Kff1 and Kff2 are set to 1 and J/Ka isapproximated to 0, the block diagram of FIG. 23(a) is approximated tothat of FIG. 23(b).

FIGS. 24 to 28 are graphs showing manners of variations of the positioncommand θr and the position response θL in the positioning servocontroller of FIG. 21.

In FIGS. 24 to 28, the position command θr in which theacceleration/deceleration time of the motor is S-shapedacceleration/deceleration of 0.03 [sec], the traveling time of the motor4 is 0.06 [sec], and the rotation angle of the motor 4 is 3 [rad] isinput to the positioning servo controller.

In FIGS. 24 to 28, acceleration is started at 0 sec. and the positioncommand θr is 3 [rad] at 0.06 sec. This time is set as the command endtime.

In FIGS. 24 to 28, if the error between the position command θr and theposition response θL is within the positioning completion width,positioning of the position response θL is deemed to be completed, andthe time from the command end time to completion of positioning is setas the setting time.

The positioning completion width is set to ±0.5 [rad].

FIG. 24 shows the manner of variations of the position response θL inthe case where the mechanical system 11 is a mechanical system of highrigidity, ω=300, and ζ=0.01.

The control parameters are set so that Kp=20, Kv=60, Kg=2, andfeedforward gains Kff1 and Kff2=1.

As shown in FIG. 24, after the command end time, the oscillation of theposition response θL is within the positioning completion width, and thepositioning of the position response θL is already completed at thecommand end time. In this case, therefore, the setting time is 0 sec.

When the rigidity of the mechanical system 11 is low, ω=100, and thevalues of the control parameters are identical with the conditions ofFIG. 24, a large oscillation having the amplitude shown in FIG. 25 isgenerated in the position response θL.

In such a case, usually, the value of the adjustment gain Kg in thecontrol parameters is reduced in order to suppress the oscillation.

FIG. 26 is a graph showing the manner of variations of the positionresponse θL in the case where, in the mechanical system 11 of lowrigidity in the same manner as FIG. 25, the value of the adjustment gainKg in the control parameters of FIG. 25 is reduced from 2 to 1.

As shown in FIG. 26, however, the oscillation of the position responseθL remains not to converge, and the positioning of the position responseθL is not completed even after elapse of 0.14 sec from the command end.

Therefore, the values of the feedforward gains Kff1 and kff2 are thenreduced. FIG. 27 is a graph showing the manner of variations of theposition response θL in the case where, in the mechanical system 11 oflow rigidity in the same manner as FIG. 26, the values of thefeedforward gains Kff1 and kff2 in the control parameters of FIG. 26 arechanged from 1 to 0.

As shown in FIG. 27, when the feedforward gains Kff1 and kff2 are set to0, the amplitude of the oscillation of the position response θL isreduced, and the oscillation converges within the positioning completionwidth, and the setting time is about 0.012 sec.

When the feedforward gains Kff1 and kff2 are set to 0, however, theeffect of the feedforward control is thoroughly lost.

Therefore, the feedforward gains Kff1 and kff2 and the adjustment gainKg are again adjusted by try and error to conduct optimum adjustment ofthe positioning of the position response θL.

FIG. 28 is a graph showing the manner of variations of the positionresponse θL in the case where the feedforward gains Kff1 and kff2=0.5and the adjustment gain Kg=1.5.

In this case, the amplitude of the oscillation of the position responseθL is smaller than the positioning completion width, and the settingtime is 0.

As described above, in the above-mentioned positioning servo controller,optimum adjustment of the positioning state is conducted while adjustingthe values of the adjustment gain Kg, the speed feedforward gain Kff1,and the acceleration feedforward gain Kff2.

However, the control parameters are adjusted by try and error, and hencethere is a problem in that the adjustment requires a prolonged timeperiod.

As described above, in the above-mentioned positioning servo controller,optimum adjustment of the positioning state is conducted while adjustingthe adjustment gain and the feedforward gains by try and error, andhence there is a problem in that the adjustment requires a prolongedtime period.

Therefore, it is an object of the invention to provide a positioningservo controller in which optimum adjustment of the positioning statecan be easily conducted.

In order to solve the problems, the positioning servo controllercomprises: a position controlling section which amplifies a positiondeviation between a position command issued from a higher-level unit anda position of a controlled object, by a position loop gain, and whichoutputs the amplified deviation; a first amplifying section whichamplifies the value output from the position controlling section by anadjustment gain, and which outputs the amplified value; a speedfeedforward controlling section which sets a value that is obtained byadding a first feedforward compensation amount to the value output fromthe first amplifying section, as a speed command, the first feedforwardcompensation amount being obtained by amplifying a differential value ofthe position command by a first feedforward gain; a speed controllingsection which amplifies a speed deviation between the speed command anda speed of the controlled object by a speed loop gain, and which outputsthe amplified deviation; a second amplifying section which amplifies thevalue output from the speed controlling section by the adjustment gain,and which outputs the amplified value; an acceleration feedforwardsection which sets a value that is obtained by adding a secondfeedforward compensation amount to the value output from the secondamplifying section, as an acceleration command, the second feedforwardcompensation amount being obtained by amplifying a differential value ofthe first feedforward compensation amount by a second feedforward gain;an acceleration controlling section which amplifies an accelerationdeviation between the acceleration command and an acceleration of thecontrolled object by an acceleration loop gain, and which outputs theamplified deviation as a torque command; and a torque amplifier whichdrives the controlled object on the basis of the torque command,

values of the first feedforward gain and the second feedforward gainbeing values of functions in which a value of the adjustment gain isused as an argument.

In the positioning servo controller of the invention, the values of thefirst feedforward gain and the second feedforward gain are those offunctions in which the adjustment gain is used as an argument, therebyenabling optimization of the positioning state to be conducted simply byadjusting the adjustment gain. Therefore, optimum adjustment of thepositioning state can be easily conducted.

Next, a positioning servo controller of an embodiment of the inventionwill be described in detail with reference to the drawings.

FIGS. 29(a) and 29(b) are the control block diagram showing theconfiguration of the positioning servo controller of the embodiment. Thepositioning servo controller of the embodiment is different from thepositioning servo controller of FIG. 21 in that a speed feedforwardcontroller 12 and an acceleration feedforward controller 13 are disposedin place of the speed feedforward controller 6 and the accelerationfeedforward controller 7.

The feedforward controllers 12 and 13 conduct a feedforward control byusing the feedforward gains Kff1 and kff2. The values of the feedforwardgains Kff1 and kff2 are those of monotone increasing functions K1(Kg)and K2(Kg) indicated by expressions (28) and (29) in which theadjustment gain Kg is used as an argument.

Kff 1 =K 1(Kg)  (28)

Kff 2 =K 2(Kg)  (29)

where

(Kg−Kg min)/(Kg max−Kg min)(Kg min≦Kg≦g max) K 1=1(Kg>Kg max)

 (Kg−Kg min)/(Kg max−Kg min(Kg min≦Kg≦g max) K 2=1(Kg>Kg max)

In the expressions, Kg min and Kg max are predetermined values whichsatisfy Kg min<Kg max, and Kg min is the minimum value of Kg.

In the positioning servo controller of Embodiment 4, even when themechanical system has low rigidity and an oscillation of a largeamplitude occurs in the position response θL as shown in FIG. 25, alsothe values of the feedforward gains Kff1 and kff2 can be simultaneouslychanged by changing the value of the adjustment gain Kg. Therefore, thepositioning state of the mechanical system can be easily adjusted to theoptimum state such as shown in FIGS. 23(a) and 23(b), simply byadjusting the adjustment gain Kg.

In the positioning servo controller of Embodiment 4, the functions K1and K2 of the feedforward gains are monotone increasing functions. Thescope of the invention is not restricted to this. The functions K1 andK2 of the feedforward gains may be curves as far as they are monotoneincreasing functions.

As described above, in the positioning servo controller of theinvention, the values of the feedforward gains are those of functions inwhich the adjustment gain is used as an argument, so that, in adjustmentof the positioning state of the position response, it is not required toseparately adjust a plurality of control parameters. Therefore, optimumadjustment of the positioning state of a mechanical system can be easilyconducted.

INDUSTRIAL APPLICABILITY

As described above, the positioning servo controller of the firstinvention comprises the acceleration controller which outputs the valuethat is obtained by amplifying the acceleration deviation between theacceleration command and the actual acceleration of the motor by theacceleration loop gain, as the torque command. Even when the inertia ofthe motor contained in the coefficient of the transfer function in whichthe position command is an input and the position response is an outputis unknown, therefore, the value of the acceleration loop gain in thetransfer function is a denominator of the inertia of the motor.Consequently, an influence of the inertia of the motor on the positionresponse can be made negligible by setting the value of the accelerationloop gain to an adequate one. In the positioning servo controller of theinvention, therefore, a satisfactory control response can be obtained.

According to the second invention, the response characteristic can beadjusted simply by adjusting one parameter, and hence the effect that arequested response characteristic can be easily realized is attained.

According to the third invention 3, both the gains of the feedback andfeedforward control systems can be adjusted simply by adjusting oneparameter, to adjust the response waveform, and hence it is possible toattain an effect that a requested response characteristic can be easilyrealized even in the case of adjustment of the disturbance response.

In the positioning servo controller of the fourth invention, the valuesof the feedforward gains are those of functions in which the adjustmentgain is used as an argument, so that, in adjustment of the positioningstate of the position response, it is not required to separately adjusta plurality of control parameters. Therefore, optimum adjustment of thepositioning state of a mechanical system can be easily conducted.

What is claimed is:
 1. A positioning servo controller comprising: aposition controlling section which amplifies a position deviationbetween a position command issued from a higher-level unit and aposition of a controlled object by a position loop gain, and whichoutputs the amplified deviation; a speed feedforward controlling sectionwhich sets a value that is obtained by adding a first feedforwardcompensation amount to the value output from said position controllingsection, as a speed command, the first feedforward compensation amountbeing obtained by amplifying a differential value of the positioncommand by a first feedforward gain; a speed controlling section whichamplifies a speed deviation between the speed command and a speed ofsaid controlled object by a speed loop gain, and which outputs theamplified deviation; an acceleration feedforward controlling sectionwhich sets a value that is obtained by adding a second feedforwardcompensation amount to the value output from said speed controllingsection, as an acceleration command, the second feedforward compensationamount being obtained by amplifying a differential value of the firstfeedforward compensation amount by a second feedforward gain; anacceleration controlling section which amplifies an accelerationdeviation between the acceleration command and an acceleration of saidcontrolled object by an acceleration loop gain, and which outputs theamplified deviation as a torque command; and a torque amplifier whichdrives said controlled object on the basis of the torque command.
 2. Apositioning servo controller comprising: a position controlling sectionwhich amplifies a position deviation between a position command issuedfrom a higher-level unit and a position of a controlled object by aposition loop gain, and which outputs the amplified deviation; a firstamplifying section which amplifies the value output from said positioncontrolling section by an adjustment gain, and which outputs theamplified value as a speed command; a differentiating section whichdifferentiates the position of said controlled object to obtain a speedof said controlled object; a speed controlling section which amplifies aspeed deviation between the speed command and the speed of saidcontrolled object obtained by said differentiating section, by a speedloop gain, and which outputs the amplified deviation; a secondamplifying section which amplifies the value output from said speedcontrolling section by the adjustment gain, and which outputs theamplified value as a torque command; and a torque amplifier which drivessaid controlled object on the basis of the torque command.
 3. Apositioning servo controller comprising: a position controlling sectionwhich amplifies a position deviation between a position command issuedfrom a higher-level unit and a position of a controlled object by aposition loop gain, and which outputs the amplified deviation; a firstamplifying section which amplifies the value output from said positioncontrolling section by an adjustment gain, and which outputs theamplified value as a speed command; a differentiating section whichdifferentiates the position of said controlled object to obtain a speedof said controlled object; an integrating section which integrates aspeed deviation between the speed command and the speed of saidcontrolled object that is obtained by said differentiating section, andwhich outputs a value that is obtained by multiplying an integral valuewith a speed loop integral gain; a second amplifying section whichamplifies the value output from said integrating section by theadjustment gain, and which outputs the amplified value; a speedcontrolling section which amplifies a value that is obtained by addingthe value output from said second amplifying section to a speeddeviation between the speed command and the speed of said controlledobject obtained by said differentiating section, by a speed loop gain,and which outputs the amplified deviation; a third amplifying sectionwhich amplifies the value output from said speed controlling section bythe adjustment gain, and which outputs the amplified value as a torquecommand; and a torque amplifier which drives said controlled object onthe basis of the torque command.
 4. A positioning servo controllercomprising: a position controlling section which amplifies a positiondeviation between a position command issued from a higher-level unit anda position of a controlled object by a position loop gain, and whichoutputs the amplified deviation; a first amplifying section whichamplifies the value output from said position controlling section by anadjustment gain, and which outputs the amplified value as a speedcommand; a differentiating section which differentiates the position ofsaid controlled object to obtain a speed of said controlled object; anintegrating section which integrates a speed deviation between the speedcommand and the speed of said controlled object that is obtained by saiddifferentiating section, and which outputs a value that is obtained bymultiplying an integral value with a speed loop integral gain; a secondamplifying section which amplifies the value output from saidintegrating section by the adjustment gain, and which outputs theamplified value; a speed controlling section which amplifies a deviationbetween the value output from said second amplifying section and thespeed of said controlled object by a speed loop gain, and which outputsthe amplified deviation; a third amplifying section which amplifies thevalue output from said speed controlling section by the adjustment gain,and which outputs the amplified value as a torque command; and a torqueamplifier which drives said controlled object on the basis of the torquecommand.
 5. A positioning servo controller comprising: a positioncontrolling section which amplifies a position deviation between aposition command issued from a higher-level unit and a position of acontrolled object, by a proportional gain, and which outputs theamplified deviation; a first amplifying section which amplifies thevalue output from said position controlling section by a value that isobtained by squaring an adjustment gain, and which outputs the amplifiedvalue; a differentiating section which differentiates the positiondeviation between the position command and said controlled object; aspeed controlling section which amplifies a value obtained by saiddifferentiating section, by a differential gain, and which outputs theamplified value; a second amplifying section which amplifies the valueoutput from said speed controlling section by the adjustment gain, andwhich outputs the amplified value; a feedforward controlling sectionwhich outputs a value that is obtained by adding a value obtained byamplifying a value obtained by second-order differentiation of theposition command, by a first feedforward gain, to a value obtained byamplifying a value obtained by differentiating the position command, bya second feedforward gain and the adjustment gain; and a torqueamplifier which sets a value obtained by adding together the valuesoutput from said first and second amplifying sections and saidfeedforward section, as a torque command, and which drives saidcontrolled object on the basis of the torque command.
 6. A positioningservo controller comprising: a position controlling section whichamplifies a position deviation between a position command issued from ahigher-level unit and a position of a controlled object, by aproportional gain, and which outputs the amplified deviation; a firstamplifying section which amplifies the value output from said positioncontrolling section by a value that is obtained by squaring anadjustment gain, and which outputs the amplified value; adifferentiating section which differentiates the position deviationbetween the position command and said controlled object; a speedcontrolling section which amplifies a value obtained by saiddifferentiating section, by a differential gain, and which outputs theamplified value; a second amplifying section which amplifies the valueoutput from said speed controlling section by the adjustment gain, andwhich outputs the amplified value; an integrating section whichintegrates the position deviation between the position command and saidcontrolled object; an integration controlling section which amplifies avalue obtained by said integrating section, by an integral gain, andwhich outputs the amplitude value; a third amplifying section whichamplifies the value output from said integration controlling section, bya value that is obtained by cubing the adjustment gain, and whichoutputs the amplified value; a feedforward controlling section whichoutputs a value that is obtained by adding together a value obtained byamplifying a value obtained by second-order differentiation of theposition command, by a first feedforward gain, a value obtained byamplifying a value obtained by differentiating the position command, bya second feedforward gain and the adjustment gain, and a value obtainedby amplifying the position command by a third feedforward gain and avalue obtained by squaring the adjustment gain; and a torque amplifierwhich sets a value obtained by adding together the values output fromsaid first, second, and third amplifying sections and said feedforwardsection, as a torque command, and which drives said controlled object onthe basis of the torque command.
 7. A positioning servo controllercomprising: a position controlling section which amplifies a positiondeviation between a position command issued from a higher-level unit anda position of a controlled object, by a proportional gain, and whichoutputs the amplified deviation; a first amplifying section whichamplifies the value output from said position controlling section by avalue that is obtained by squaring an adjustment gain, and which outputsthe amplified value; a differentiating section which differentiates theposition deviation between the position command and said controlledobject; a speed controlling section which amplifies a value obtained bysaid differentiating section, by a differential gain, and which outputsthe amplified value; a second amplifying section which amplifies thevalue output from said speed controlling section by the adjustment gain,and which outputs the amplified value; an integrating section whichintegrates the position deviation between the position command and saidcontrolled object; an integration controlling section which amplifies avalue obtained by said integrating section, by an integral gain, andwhich outputs the amplitude value; a third amplifying section whichamplifies a value output from said integration controlling section, by avalue that is obtained by cubing the adjustment gain, and which outputsthe amplified value; a second-order differentiating section whichperforms second-order differentiation on the position deviation betweenthe position command and said controlled object; an accelerationcontrolling section which amplifies a value obtained by saidsecond-order differentiating section, by an acceleration gain, and whichoutputs the amplified value; a feedforward controlling section whichoutputs a value that is obtained by adding together a value obtained byamplifying a value obtained by second-order differentiation of theposition command, by a first feedforward gain, a value obtained byamplifying a value obtained by differentiating the position command, bya second feedforward gain and the adjustment gain, and a value obtainedby amplifying the position command by a third feedforward gain and avalue obtained by squaring the adjustment gain; and a torque amplifierwhich sets a value obtained by adding together the values output fromsaid first, second, and third amplifying sections, said accelerationcontrolling section, and said feedforward section, as a torque command,and which drives said controlled object on the basis of the torquecommand.
 8. A positioning servo controller comprising: a positioncontrolling section which amplifies a position deviation between aposition command issued from a higher-level unit and a position of acontrolled object, by a position loop gain, and which outputs theamplified deviation; a first amplifying section which amplifies thevalue output from said position controlling section by an adjustmentgain, and which outputs the amplified value; a speed feedforwardcontrolling section which sets a value that is obtained by adding afirst feedforward compensation amount to the value output from saidfirst amplifying section, as a speed command, the first feedforwardcompensation amount being obtained by amplifying a differential value ofthe position command by a first feedforward gain; a speed controllingsection which amplifies a speed deviation between the speed command anda speed of said controlled object by a speed loop gain, and whichoutputs the amplified deviation; a second amplifying section whichamplifies the value output from said speed controlling section by theadjustment gain, and which outputs the amplified value; an accelerationfeedforward section which sets a value that is obtained by adding asecond feedforward compensation amount to the value output from saidsecond amplifying section, as an acceleration command, the secondfeedforward compensation amount being obtained by amplifying adifferential value of the first feedforward compensation amount by asecond feedforward gain; an acceleration controlling section whichamplifies an acceleration deviation between the acceleration command andan acceleration of said controlled object by an acceleration loop gain,and which outputs the amplified deviation as a torque command; and atorque amplifier which drives said controlled object on the basis of thetorque command, values of the first feedforward gain and the secondfeedforward gain being values of functions in which a value of theadjustment gain is used as an argument.